It sounds like a ‘classic rollover effect bug’ to me: if you trigger a visual effect on any link (or ‘button’) either with jQuery or JavaScript, users on touch devices may be forced to click twice: “iPad/iPhone hover problem causes the user to double click a link“
I suggest you either try to replace the ‘mouseover’ effects with css :hover effects or trigger the jQuery event only, if the user is not on a touch device.
A third way can be found on the page over at stackexchange that I linked above: add a jquery snippet that tells the (iOS) browser the link was actually clicked.
PS: it could be useful anyways if you could either provide code or name any of the contact form plugins you used.